Line an 8x8 pan with parchment paper. Melt and slightly brown butter over low heat in a medium saucepan. Once butter has melted and starts to turn golden, stir in marshmallows.
Once the marshmallows have completely melted and combined with butter, add in the cereal. Using a greased spatula fold the cereal into the marshmallow.
Once the cereal has been well folded in, carefully pour the marshmallow cereal mix into the prepared pan. Be careful no to press the cereal into the pan, just lightly tap it info place.
Place the white chocolate and condensed milk into a microwave safe bowl and microwave at 30 second intervals until the chocolate is completely melted. Then drizzle it over the top of your marshmallow treats.
Notes
For St Patrick's Day I added 2 drops of green food coloring, but this is totally optional.